P01DF code meaning
Cylinder 11 Injection Timing Performance - Over Retarded
Powertrain system Generic code P01xx codes Check engine light
What P01DF means
Diesel engines must detect when fuel can no longer be injected at the correct crank angle – CARB requires this for every injector individually, hence one code per cylinder. The start of injection is not measured directly: during overrun with fuel cut-off the control module fires a tiny test injection into one cylinder (GM: about 1.5 mm³) and evaluates the resulting speed change at the crankshaft sensor. From this it learns how much extra energizing time the injector needs (Bosch calls this zero fuel calibration). This code means injector 11 needs clearly more energizing time than intended, i.e. it opens too late – GM sets it above 80 µs of extra time, after two trips. No manufacturer document using the codes for cylinders 9–12 was found; the description follows CARB's requirement and the documented measuring principle (Bosch patent, GM tables for cylinders 1–8). Such codes can only appear on engines with at least that many cylinders.
P01DF at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.5 to 4 hours
- Clears after repairAfter a drive cycle
Symptoms of P01DF
- Check engine light on (after two drive cycles)
- Louder combustion noise or knocking
- Rough idle
- Possibly smoke
Common causes of P01DF
- Most likelyInjector worn, coked or sticking (opens late, delivers too little)
- PossibleFalse setting from software or vehicle vibration (e.g. off-road tires)
- PossibleWrong injector correction code stored after an injector replacement
- Less likelyBoost leak or loose injector clamp
- Less likelyContaminated fuel
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Fuel injector cylinder 11Crankshaft position sensorEngine control module
What each part of P01DF means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| DF | The exact fault in that area. |
What to do next
- Note P01DF and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P01DF
What does P01DF mean?
P01DF means "Cylinder 11 Injection Timing Performance - Over Retarded". Diesel engines must detect when fuel can no longer be injected at the correct crank angle – CARB requires this for every injector individually, hence one code per cylinder. It is a generic code, so it means the same on every make.
Is it safe to drive with P01DF?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P01DF fail an emissions test?
Yes, it can. P01DF is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P01DF to fix?
Difficulty: hard. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P01DF clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.